Carrier route record

OOSEA→ONT

SkyWest Airlines · Seattle to Ontario

Flights: 1,084
Period: July 2025 to June 2026
Share of route: 43%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with SkyWest Airlines.

SkyWest on SEA to ONT earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 12 points better than the national rate of 77.6%. When something does go wrong the average delay runs roughly 50 minutes. That rests on 1,084 flights, with a median arrival 9 minutes early.

Set against the rest of the country, SkyWest's SEA to ONT record is 12 points better than the US average of 77.6%. That gap is worth roughly 121 fewer late arrivals for every thousand flights.

On time

89.7%

Arrivals under 15 minutes late, of 1,080 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

0.37%

National rate is 1.81%

Whole route

82.9%

Every carrier on SEA to ONT, 2,550 flights

These figures cover 1,084 flights between July 2025 and June 2026. The median arrival is 9 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

SkyWest against every carrier on SEA to ONT

SkyWest flew 1,084 of the 2,550 flights on SEA to ONT, about 43% of it. Its 89.7% on time is 7 points better than the route as a whole, which runs 82.9%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from Delta at 93.1% to Alaska at 77.4%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on SEA to ONT
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Linesthin sample	29	93.1%	32 min	0.00%	A+
SkyWest Airlines (this page)	1,084	89.7%	52 min	0.37%	A+
Frontier Airlinesthin sample	169	78.4%	77 min	1.18%	B
Alaska Airlines	1,268	77.4%	47 min	2.05%	B

Flight by flight

SkyWest flight numbers on SEA to ONT

Departure window

When SkyWest runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 1,084 flights.

5am–8am41 flights95.1%
8am–11am286 flights91.5%
11am–2pm99 flights89.9%
2pm–5pm299 flights88.9%
5pm–8pm—
8pm–5am359 flights88.3%

Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.

The early departures do better, though not dramatically: 95.1% on time for the 5am–8am window against 88.3% for 8pm–5am. Worth taking if the schedule allows, not worth an extra connection. The 8pm–5am window is the busiest, with 359 flights scheduled in it.

Across the year

SkyWest on SEA to ONT through the year

Darker means more delays. Figures are on-time percentages.October best, December worst

December is the weak month at 82.2% on time, against 93.5% in October. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. May was the busiest month here, with 124 flights.

Across the week, Saturday is the strongest day at 93.4% on time and Friday the weakest at 86.1%. 7 points is a smaller lever than departure hour, but it is free.

Delay causes

Why SkyWest runs late on this route

One category carries most of the weight here. Carrier accounts for 64% of the 5,751 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Carrier
64%
Extreme weather
26%
National Airspace System
10%

Extreme weather accounts for 26% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 4.1 times the usual weather exposure. The split is drawn from 5,751 reported delay minutes.

The largest share of delay minutes, 64%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 3,693 of the 5,751 delay minutes reported here.

Cancellations are rare at 0.37%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 2.4% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

The 956 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg runs 92.1% on time across 1,085 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 1,084 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking SkyWest on SEA to ONT

Put together: treat all of this as provisional. 1,084 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 89.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,080 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures